High energy radiation stabilization of cellulose obtained by esterifying with thenoyl chloride

ABSTRACT

THIS INVENTION RELATES TO A METHOD FOR STABILIZING ORGANIC MATERIALS THAT CONTAIN THE GLYCOSIDIC BOND TO THE EFFECT OF HIGH ENERGY RADIATION. STABILIZATION IS ACHIEVED BY THE INTRODUCTION OF THENOATE GROUPS AS SUBSTITUENTS INTO THE SAID ORGANIC MATERIAL. THE METHOD OF THIS INVENTION HAS AS ITS OBJECT THE MODIFICATION OF THE CHEMICAL STRUCTURE OF ORGANIC MATERIALS WHIC CONTAIN THE GLYCOL BOND TO ALLOW PERFERENTIAL TRANSFER OF HIGH ENERGY FROM ONE PART OF THE ORGANIC MATERIAL TO THE THENOATE SUBSTITUENT GROUP WITHIN WHICH GROUP RADIATION ENERGY IS DISSIPATED WITHOUT DAMAGE OT THE GLYCOSIDIC BOND OF THE ORGANIC MATERIALS.

United States Patent 01 fice 3,676,056 Patented July 11, 1972 HIGHENERGY RADIATION STABILIZATION OF CELLULOSE OBTAINED BY ESTERIFYING WITHTHENOYL CHLORIDE Jett C. Arthur, Jr., Metairie, La., and Sujan Singh,Varanasi Uttar Pradesh, India, assignors to the United States of Americaas represented by the Secretary of Agriculture No Drawing. Filed Apr.30, 1971, Ser. No. 139,138

Int. Cl. D06m 13/20 US. Cl. 8-120 9 Claims ABSTRACT OF THE DISCLOSUREThis invention relates to a method for stabilizing organic materialsthat contain the glycosidic bond to the eifects of high energyradiation. Stabilization is achieved by the introduction of thenoategroups as substituents into the said organic material. The method ofthis invention has as its objective the modification of the chemicalstructure of organic materials which contain the glycosidic bond toallow preferential transfer of high energy from one part of the organicmaterial to the thenoate substituent group within which group radiationenergy is dissipated without damage to the glycosidic bond of theorganic material.

A non-exclusive, irrevocable, royalty-free license in the inventionherein described, throughout the world for all purposes of the UnitedStates Government, with the power to grant subliceuses for suchpurposes, is hereby granted to the Government of the United States ofAmerica.

This instant invention relates to a process for the preparation ofcotton textile products, wherein the macromolecular and morphologicalproperties of cotton are selectively and permanently stabilized to thedegradative effects of high energy radiation, so that said textileproducts could be used in manufacturing processes in which high energyradiation is employed in one of the unit operations such as insterilization and copolymerization processes. The method of thisinvention has as its objective the modification of the chemicalstructure of cotton fibers, mechanically organized into textileproducts, so that the natural properties of cotton are conserved to amaximum extent while imparting high energy radiation resistance andstabilization to the resulting all cotton textile products.

Developments in the commercial use of high energy radiation, forexample, in sterilization of medical and personal products, preparationof copolymers of wood block flooring, curing of coatings, anddurable-press textile processing, are currently of great interest. Sincecellulose is by far the most widely used polymer in most of thesecommercial applications, the effects of high energy radiation on themacromolecular properties of cellulose are of prime interest. Cellulosebelongs to that class of polymers, which on exposure to high energyradiation, oxidatively depolymerizes by cleavage of the glycosidic bond.

High energy radiation, which interacts in a chemically non-specificmanner with compounds containing elements of low atomic number, such ascellulose, ionizes the com pound. That is, a spur of secondary electronsis formed. The localization of energy from these secondary electronsinitiates practically all of the observable chemical effects ofradiation on compounds. If the energy from these secondary electronscould be selectively absorbed and dissipated as heat or light, thelocalization of energy that initiates glycosidic bond cleavage would beeliminated or at least minimized. Therefore, cellulose could bestabilized or made resistant to the degradative effects of high energyradiation. We have previously shown (US. Pat. No. 3,519,382) that theintroduction of aromatic groups as substituents on the cellulosemolecule stabilized the cellulosic polymer to the degradative effects ofhigh energy radiation.

The instant invention defines another class of substituent groups, whichwhen introduced into cellulose, stabilize cellulose to the degradativeeffects of high energy radiation. Whereas aromatic groups are cycliccompounds containing six carbon atoms, thenoate groups are heterocycliccompounds containing four carbon atoms and one sulfur atom. Unexpectedlyit was found that when thenoate groups were introduced as substituentson cotton cellulose, these groups selectively absorbed and dissipatedthe energy from the secondary electrons thereby minimizing glycosidicbond cleavage and stabilizing cotton to high energy radiation. In thecase of aromatic groups, we found that some types of covalent linkagesbonding the groups to cellulose were not stable to high energyradiation; in such cases when the covalent bonds were broken, theradiation stabilization eifects of aromatic groups on cellulose werelost. In the case of thenoate groups evaluated, the covalent bondsbetween the thenoate groups and cellulose were apparently stable to highenergy radiation; therefore, the radiation stabilization elfects oncellulose of all of thenoate groups evaluated were retained on exposureto high energy radiation.

The following examples set forth the invention in more detail.

EXAMPLE 1 Purified fibrous cotton (8 parts) in the form of 7s/3 yarn (aconvenient textile product for handling and testing), which had beendried in air at 60 C. for 2 hours, was placed in a reaction flask withN,N-dimethylformamide solvent (200 parts). Then thenoyl chloride andpyridine were added to the contents of the reaction flask and stirredand heated at C. for the desired reaction time. Then the yarn productswere Washed twice with N,N-dimethylformamide solvent parts); immersed inmethanol (100 parts) at 60 C. for 30 minutes; then treated withpotassium bicarbonate solution (10 percent concentration) at 25 C. for30 minutes; followed by washing with water. The yarn products werestretched overnight to about 85 percent of their original lengths andthen dried at 25 C. and 50 percent relative humidity for 24 hours.Concentrations in the reaction mixture of cotton to 2-thenoyl chlorideto pyridine (1 mole of D- glucose residue of cotton:2 moles of Z-thenoylchloride:4 moles of pyridine) after 24 hours of reaction time gave athenoated yarn product with a degree of substitution of 0.21 thenoategroup per glucose residue of cotton. The initial strength of thethenoated cotton yarn product was 8.5 pounds; after exposure to gammaradiation from cobalt-60 (a convenient source of high energy radiation)in air to a dosage of 1.3 10 e.v./g., the strength of the irradiated,thenoated cotton yarn was 4.6 pounds. Untreated cotton yarn had astrength of 10.4 pounds; after irradiation to the same dosage thestrength of irradiated, untreated yarn was 2.2 pounds. Protection fromradiation damage is indicated by the facts (1) that the thenoated cottonyarn (degree of substitution 0.21) retained 53 percent of its originalstrength on irradiation and (2) that untreated cotton yarn retained only21 percent of its original strength on irradiation.

EXAMPLE 2 The method of Example 1, except that S-methyl-Z- thenoylchloride was used and except that concentrations in the reaction mixtureof cotton to 5-methyl-2-thenoyl chloride to pyridine were 1 mole ofD-glucose residue of cotton to 4 moles of S-methyl-Z-thenoyl chloride to8 moles of pyridine. After 24 hours of reaction time, a 5-methyl-Z-thenoated cotton product with a degree of substitution of 0.56S-methyl-Z-t-henoate group per glucose residue of cotton was obtained.The initial strength of this yarn product was 7.6 pounds; after exposureto radiation as in Example 1, the strength of the irradiated yarnproduct was 6.1 pounds. Protection from radiation damage is indicated bythe facts (1) that the 5-methyl-2-thenoated cotton yarn retained 80percent of its original strength on irradiation and (2) that untreatedcotton yarn retained only 21 percent of its original strength onirradiation.

EXAMPLE 3 The method of Example 1, except that Z-thiopheneacryloylchloride was used and except that concentrations in the reaction mixtureof cotton to 2-thiopheneacryloyl chloride to pyridine were 1 mole ofD-glucose residue of cotton to 3 moles of 2-thiopheneacryloyl chlorideto 6 moles of pyridine. After 24 hours of reaction time, a 2-thiopheneacryloylated cotton product with a degree of substitution of1.43 2-thiopheneacryloy1ate groups per glucose residue of cotton wasobtained. The initial strength of this yarn product was 9.7 pounds;after exposure to radiation as in Example 1, the strength of theirradiated, yarn product was 6.1 pounds. Protection from radiationdamage is indicated by the facts (1) that the 2- thiopheneacryloylatedcotton yarn retained 62 percent of its original strength on irradiationand (2) that untreated cotton yarn retained only 21 percent of itsoriginal strength on irradiation.

EXAMPLE 4 The method of Example 1, except that 5-bromo-2- thenoylchloride was used and except that concentrations in the reaction mixtureof cotton to 5-bromo-2-thenoyl chloride to pyridine were 1 mole ofD-glucose residue of cotton to 4 moles of 5-bromo-2-thenoyl chloride to8 moles of pyridine. After 24 hours of reaction time, a 5-bromo-Z-thenoylated cotton product with an add-on (increase in weight)of 80 percent was obtained. The initial strength of this yarn productwas 10.5 pounds; after exposure to radiation as in Example 1, thestrength of the irradiated yarn product was 5.7 pounds. Protection fromradiation damage is indicated by the facts (1) that the 455-bromo-2-thenoated cotton yarn retained 55 percent of its originalstrength on irradiation and (2) that untreated cotton yarn retained only21 percent of its original strength on irradiation.

EXAMPLE 5 The method of Example 1, except thatS-bromo-Z-thiopheneacryloyl chloride was used and except thatconcentrations in the reaction mixture of cotton to 5-bromo-2-thiopheneacryloyl chloride to pyridine were 1 mole of D- glucose residueof cotton to 4 moles of S-bromo-Z-thiopheneacryloyl chloride to 8 molesof pyridine. After 24 hours of reaction time, a5-bromo-2-thiopheneacryloylated cotton product with an add-on (increasein weight) of 5 250 percent was obtained. The initial strength of thisyarn product was 4.8 pounds; after exposure to radiation as in Example1, the strength of the irradiated yarn product was 4.0 pounds.Protection from radiation damage is indicated by the facts (1) that the5-bromo-2thiopheneacryloylated cotton yarn retained 84 percent of itsoriginal strength on irradiation and (2) that untreated cotton yarnretained only 21 percent of its original strength on irradiation.

We claim:

1. A method of improving the degradation-resistance of cotton yarn uponthe exposure of said yarn to high energy radiation comprising:

(a) drying cotton yarn in air,

(b) esterifying the dried cotton yarn with a thenoyl chloride selectedfrom the group consisting of 2- thenoyl chloride, S-methyI-Z-thenoylchloride, 2- thiopheneacryloyl chloride, 5-bromo-2-thenoyl chloride, and5-bromo-2-thiopheneacryloyl chloride,

() washing the thenoylated cotton yarn from (b) free of excess reagents,

(d) restretching the washed, thenoylated cotton yarn to approximatelyits initial length before reaction and drying the stretched, washedyarn.

2. The method of claim 1 wherein the thenoyl chloride is 2-thenoylchloride.

3. The method of claim 1 wherein the thenoyl chloride is-rnethyl-2-thenoyl chloride.

4. The method of claim 1 wherein the thenoyl chloride is2-thiopheneacryloyl chloride.

5. The method of claim 1 wherein the thenoyl chloride is5-bromo-2-thenoyl chloride.

6. The method of claim 1 wherein the thenoyl chloride is5-brorno-2-thiopheneacryloyl chloride.

7. The product of claim 2.

8. The product of claim 3.

9. The product of claim 4.

References Cited UNITED STATES PATENTS 3,519,382 7/1970 Arthur et a1.8l20 FOREIGN PATENTS 645,539 7/1962 Canada 8l'20 CHARLES VAN HORN,Primary Examiner J. CANNON, Assistant Examiner US. Cl. X.R. 38-144;117-447, 93.3; 204-4601; 2602l0 R, 224

